Proteomics Peptides & KitsPeptide sets and pools, as well as assay standardization kits are available with stable isotope labeled or unlabeled proteotypic peptides for mass-spectrometry based proteomics such as MRM assays.

Chelate Peptides (DOTA)DOTA is linked to molecules that have affinity for various structures (e.g. somatostatin receptors in neuroendocrine tumors). The resulting compounds can be bound to radionuclided and are used with a number of radioisotopes in cancer therapy and diagnosis

Immunology Standards & ControlsStandards and controls for reproducible T-cell assays such as ELISPOT and multimer assays. We offer a large variety of positive and negative control peptide pools for antigen specific T cell stimulation as well as kit to produce TCR-engineered reference samples for performance control.

Antigen PeptidesAntigen peptides represent specific epitopes for stimulation of T cells in T cell assays such as ELISPOT. We offer the corresponding MHC multimer for each antigen peptide. Antigens from different pathogens are available as well as tumor associated antigens.

Cosmetic PeptidesCosmetic Peptides such as Lysine and Cysteine Peptide are used for DPRA (Direct Peptide Reactivity Assay) for Skin Sensitization Testing. The DPRA measures the reaction of a chemical with synthetic peptides containing Cysteine (Ac‑RFAACAA‑COOH) or Lysine (Ac‑RFAAKAA‑COOH) to assess its sensitization potency. For research use only!

Occurrence and Detection of Phosphopeptide Isomers in Large-Scale Phosphoproteomics Experiments

The past decade has been marked by the emergence of selective affinity media and sensitive mass spectrometry instrumentation that facilitated large-scale phosphoproteome analyses and expanded the repertoire of protein phosphorylation. Despite these remarkable advances, the precise location of the phosphorylation site still represents a sizable challenge in view of the labile nature of the phosphoester bond and the presence of neighboring phosphorylatable residues within the same peptide. This difficulty is exacerbated by the combinatorial distribution of phosphorylated residues giving rise to different phosphopeptide isomers. These peptides have similar physicochemical properties, and their separation by LC is often problematic. Few studies have described the frequency and distribution of phosphoisomers in large-scale phosphoproteomics experiments, and no convenient informatics tools currently exist to facilitate their detection. To address this analytical challenge, we developed two algorithms to detect separated and co-eluting phosphopeptide isomers and target their subsequent identification using an inclusion list in LC-MS/MS experiments. Using these algorithms, we determined that the proportion of isomers present in phosphoproteomics studies from mouse, rat, and fly cell extracts represents 3-6% of all identified phosphopeptides. While conventional analysis can identify chromatographically separated phosphopeptides, targeted LC-MS/MS analyses using inclusion lists provided complementary identification and expanded the number of phosphopeptide isomers by at least 52%. Interestingly, these analyses revealed that the occurrence of phosphopeptides isomers can also correlate with the presence of extended phosphorylatable amino acids that can act as a "phosphorylation switch" to bind complementary domains such as those present in SR proteins and ribonucleoprotein complexes.